/*
** dual.c    Runs as both CONSOLE and GUI app in Windows.
**
** This solution is based on the "Momentary Flicker" solution that Robert Kennedy
** discusses in the highest-rated answer (as of Jan 2013), i.e. the one drawback
** is that the console window will briefly flash up when run as a GUI.  If you
** want to avoid this, you can create a shortcut to the executable and tell the
** short cut to run minimized.  That will minimize the console window (which then
** immediately quits), but not the GUI window.  If you want the GUI window to
** also run minimized, you have to also put -minimized on the command line.
**
** Tested under MinGW:  gcc -o dual.exe dual.c -lgdi32
**
*/
#include <windows.h>
#include <stdio.h>

static int my_win_main(HINSTANCE hInstance,int argc,char *argv[],int iCmdShow);
static LRESULT CALLBACK WndProc(HWND hwnd,UINT iMsg,WPARAM wParam,LPARAM lParam);
static int win_started_from_console(void);
static BOOL CALLBACK find_win_by_procid(HWND hwnd,LPARAM lp);

int main(int argc,char *argv[])

    {
    HINSTANCE hinst;
    int i,gui,relaunch,minimized,started_from_console;

    /*
    ** If not run from command-line, or if run with "-gui" option, then GUI mode
    ** Otherwise, CONSOLE app.
    */
    started_from_console = win_started_from_console();
    gui = !started_from_console;
    relaunch=0;
    minimized=0;
    /*
    ** Check command options for forced GUI and/or re-launch
    */
    for (i=1;i<argc;i++)
        {
        if (!strcmp(argv[i],"-minimized"))
            minimized=1;
        if (!strcmp(argv[i],"-gui"))
            gui=1;
        if (!strcmp(argv[i],"-gui-"))
            gui=0;
        if (!strcmp(argv[i],"-relaunch"))
            relaunch=1;
        }
    if (!gui && !relaunch)
        {
        /* RUN AS CONSOLE APP */
        printf("Console app only.\n");
        printf("Usage:  dual [-gui[-]] [-minimized].\n\n");
        if (!started_from_console)
            {
            char buf[16];
            printf("Press <Enter> to exit.\n");
            fgets(buf,15,stdin);
            }
        return(0);
        }

    /* GUI mode */
    /*
    ** If started from CONSOLE, but want to run in GUI mode, need to re-launch
    ** application to completely separate it from the console that started it.
    **
    ** Technically, we don't have to re-launch if we are not started from
    ** a console to begin with, but by re-launching we can avoid the flicker of
    ** the console window when we start if we start from a shortcut which tells
    ** us to run minimized.
    **
    ** If the user puts "-minimized" on the command-line, then there's
    ** no point to re-launching when double-clicked.
    */
    if (!relaunch && (started_from_console || !minimized))
        {
        char exename[256];
        char buf[512];
        STARTUPINFO si;
        PROCESS_INFORMATION pi;

        GetStartupInfo(&si);
        GetModuleFileNameA(NULL,exename,255);
        sprintf(buf,"\"%s\" -relaunch",exename);
        for (i=1;i<argc;i++)
            {
            if (strlen(argv[i])+3+strlen(buf) > 511)
                break;
            sprintf(&buf[strlen(buf)]," \"%s\"",argv[i]);
            }
        memset(&pi,0,sizeof(PROCESS_INFORMATION));
        memset(&si,0,sizeof(STARTUPINFO));
        si.cb = sizeof(STARTUPINFO);
        si.dwX = 0; /* Ignored unless si.dwFlags |= STARTF_USEPOSITION */
        si.dwY = 0;
        si.dwXSize = 0; /* Ignored unless si.dwFlags |= STARTF_USESIZE */
        si.dwYSize = 0;
        si.dwFlags = STARTF_USESHOWWINDOW;
        si.wShowWindow = SW_SHOWNORMAL;
        /*
        ** Note that launching ourselves from a console will NOT create new console.
        */
        CreateProcess(exename,buf,0,0,1,DETACHED_PROCESS,0,NULL,&si,&pi);
        return(10); /* Re-launched return code */
        }
    /*
    ** GUI code starts here
    */
    hinst=GetModuleHandle(NULL);
    /* Free the console that we started with */
    FreeConsole();
    /* GUI call with functionality of WinMain */
    return(my_win_main(hinst,argc,argv,minimized ? SW_MINIMIZE : SW_SHOWNORMAL));
    }


static int my_win_main(HINSTANCE hInstance,int argc,char *argv[],int iCmdShow)

    {
    HWND        hwnd;
    MSG         msg;
    WNDCLASSEX  wndclass;
    static char *wintitle="GUI Window";

    wndclass.cbSize        = sizeof (wndclass) ;
    wndclass.style         = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc   = WndProc;
    wndclass.cbClsExtra    = 0 ;
    wndclass.cbWndExtra    = 0 ;
    wndclass.hInstance     = hInstance;
    wndclass.hIcon         = NULL;
    wndclass.hCursor       = NULL;
    wndclass.hbrBackground = NULL;
    wndclass.lpszMenuName  = NULL;
    wndclass.lpszClassName = wintitle;
    wndclass.hIconSm       = NULL;
    RegisterClassEx (&wndclass) ;

    hwnd = CreateWindowEx(WS_EX_OVERLAPPEDWINDOW,wintitle,0,
                          WS_VISIBLE|WS_OVERLAPPEDWINDOW,
                          100,100,400,200,NULL,NULL,hInstance,NULL);
    SetWindowText(hwnd,wintitle);
    ShowWindow(hwnd,iCmdShow);
    while (GetMessage(&msg,NULL,0,0))
        {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
        }
    return(msg.wParam);
    }


static LRESULT CALLBACK WndProc (HWND hwnd,UINT iMsg,WPARAM wParam,LPARAM lParam)

    {
    if (iMsg==WM_DESTROY)
        {
        PostQuitMessage(0);
        return(0);
        }
    return(DefWindowProc(hwnd,iMsg,wParam,lParam));
    }


static int fwbp_pid;
static int fwbp_count;
static int win_started_from_console(void)

    {
    fwbp_pid=GetCurrentProcessId();
    if (fwbp_pid==0)
        return(0);
    fwbp_count=0;
    EnumWindows((WNDENUMPROC)find_win_by_procid,0L);
    return(fwbp_count==0);
    }


static BOOL CALLBACK find_win_by_procid(HWND hwnd,LPARAM lp)

    {
    int pid;

    GetWindowThreadProcessId(hwnd,(LPDWORD)&pid);
    if (pid==fwbp_pid)
        fwbp_count++;
    return(TRUE);
    }